1. Field of the Invention
The present invention relates to a ground terminal, a printed board mounted with a ground terminal, and a method for mounting a ground terminal to a printed board.
2. Description of the Related Art
Electronic or electrical equipment is comprised of electronic and/or electrical parts (hereinafter referred to as electronic parts) that are mounted to one or more printed boards received in a chassis. In a case where a mounter is used to mount electronic parts on a printed board, the printed board must be positioned at a predetermined part mounting position with respect to the mounter. To this end, a positioning unit for instance is employed that has a positioning pin adapted removably fitted into a positioning hole formed in the printed board. Specifically, the printed board is transported toward the mounter along guide rails of the positioning unit. When the printed board is transported to or near the predetermined part mounting position, the positioning pin is fitted into the positioning hole, whereby the printed board is positioned at the part mounting position.
A further explanation will be given with reference to FIG. 12. Reference numeral 3 denotes one of a pair of guide rails of the positioning unit. A guide groove 3a is formed in an inner side face of the guide rail 3, into which a side edge portion 2a of the printed board 2 is fitted. Reference numeral 2b denotes the positioning hole formed in the printed board 2, into which the positioning pin 4 is removably fitted. The printed board 2 is positioned at the part mounting position by inserting the positioning pin 4 into the positioning hole 2b, and electronic parts are mounted to the printed board 2 by means of the mounter.
As explained above, the printed board 2 is mounted with electronic parts in a condition that both the side edge portions 2a of the printed board 2 are covered by the guide rails 3. Thus, the side edge portions 2a of the printed board 2 constitute a dead space where no electronic parts can be mounted. To widen the part mounting area of the printed board 2, the dead space, i.e., the side edge portions 2a of the printed board 2 are made as narrow as possible. From a similar point of view, the positioning hole 2a is formed near one side edge portion 2a of the printed board 2.
The printed board is mounted with a ground terminal, which is a sort of electronic part, so as to electrically connect the printed board to the chassis through the ground terminal. Such a ground terminal is disclosed in Japanese patent publication no. 2863981, which comprises, as shown in FIG. 11, a plurality of connection portions 1a used for establishing connection between the ground terminal 1 and the printed board, and a fixture portion 1b used for screw-fastening between the ground terminal 1 and the chassis. The fixture portion 1b is formed with a screw insertion hole 1c permitting a screw to extend therethrough.
When the ground terminal 1 shown in FIG. 11 is mounted to the printed board, the ground terminal 1 is placed on the printed board in a condition that the connection portions 1a are aligned with solder portions formed in the printed board and the screw insertion hole 1c is aligned with a screw insertion hole formed in the printed board and with a tapped hole formed in the chassis. Next, the connection portions 1a of the ground terminal 1 are soldered to the solder portions of the printed board. Further, the screw inserted into the screw insertion hole of the ground terminal 1 and that of the printed board is threadedly engaged with the tapped hole of the chassis and is then fastened, to thereby secure both the ground terminal 1 and the printed board to the chassis, whereby the ground terminal 1 is electrically connected through the screw to the chassis, and the printed board is grounded to the chassis through the ground terminal 1.
As mentioned above with reference to FIG. 2, it is preferable that the part mounting area of the printed board 2 be widened. As a measure to increase the part mounting area of the printed board, the screw insertion hole of the printed board may be arranged to have a function of the positioning hole (shown at 2b in FIG. 2) in addition to its primary function of permitting the screw to extending therethrough. In this case, when the ground terminal is mounted to the printed board, the screw insertion hole (shown at 1c in FIG. 11) of the ground terminal must be aligned with the screw-insertion/positioning hole (corresponding to the hole 2b in FIG. 12) of the printed board.
In this regard, the ground terminal 1 shown in FIG. 11 has its fixture portion 1b which is large in size, and therefore, its distal end interferes with the guide rail 3 when an attempt is made to align the screw insertion hole 1c with the positioning hole 2b of the printed board 2. In other words, the ground terminal 1 cannot be mounted to the side edge portion 2a of the printed board 2 around the positioning hole 2 (more generally, to a peripheral portion of the printed board 2). In order to make the ground terminal 1 mountable to the printed board 2, on the other hand, it is essentially required to form the positioning hole 2b at a location away from the side edge portion 2a of the printed board 2, and hence the part mounting area of the printed board 2 decreases accordingly.